Manufacture of objects consisting of refractory, insulating, abrasive, or like substances



Apnl 29, 1930. M. FOURMENT A MANUFACTURE OF OBJEOTS CONSISTING OFREFRACTORY, INSULATING, ABRASIVE, OR LIKE SUBSTANCES Filed Dec. 15, 19272 Sheets-Sheet 1 g lg l M IN g MANUFACTURE OF OBJECTS CONSISTING OFREFRACTORY,

April 29, 1930. FOURMENT 1,756,457

INSULATING, ABRASIVE, OR LIKE SUBSTANCES Filed Dec. 13, 1927 2Sheets-Sheet 2 Patented Apr. 29, 1930.

PATENT OFFICE MABCEL FOUBMENT, OF PARIS, FRANCE MANUFACTURE OF OBJECTSCONSISTING OF REFRACTORY, INSULATING, ALBRASIVE,

OR LIKE SUBSTANCES Application filediDecember 13, 1927, Serial No.239,748, and in France December 21, 1928.

The present invention has for its object a process for the manufactureof objects consisting of refractory, insulating, abrasive or likesubstances, in which the objects are heated. by the use of pieces ofconducting material such as carbon, which are heated by inductioncurrents of high frequency.

- The invention further relates to apparatus by which the said processmay be carried into efi'ect.

According to the invention, such apparatus comprise a refractoryenvelope carrying a winding which is connected with a source of highfrequency electric current. In the interior of the said envelope 1dispose the object to be heated and also the piece or pieces ofconducting material such as carbon, so that the heat produced by thesaid pieces will raise the object to the proper temperature. j

It may be advantageous to render the said refractory envelope movable,as well as the said piece of conducting material, and in this case theconducting pieces are placed in the interior or at the exterior of theobject to be heated, or both in the interior and at the exterior.

Various apparatus according to the present invention are shown by way ofexample in the appended drawings.

Fig. 1 is a vertical section of the first apparatus, in which the tubeis stationary an the heating is eifectedby meansof a carbon cylinderwhich is placed in the interior of the hollow object to be manufactured.

Fig. 2 is a vertical section of a second apparatus in which the tube isstationary an the heating; is effected by a carbon cylinder placed atthe exterior of the hollow object.

Fig. 3 is a vertical'section of a third apparatus in which the tube isrotated on its axis.

' Figs. 4 and 5 are vertical sections of other forms of apparatus inwhich the relative positions of the tube and the induction winding arevariable, for the internal and external heating of objects of greatlength.

The apparatus shown in Figs. 1 and 2, is adapted for the manufacture ofa refractory crucible of cylindrical form; 1 is the inductor windingwhich may consist of a copper tube,

optionally cooled by a current of water. The

said winding is applied against the internal wall of a solid member2which may consist of cement or like material. The tube in which therefractory crucible is to be formed comprises an envelope 3 consistingof a suitable dielectric, such as fused silica, placed in contact with asecond envelope 4 consisting of a refractory and heat-insulatingsubstance. In the interior of the resulting double envelope are disposedtwo tubes 5 and 6 consisting of paper or pasteboard. The

space 11 between the said tubes contains the refractory substance ormixture of which the said crucible is to be made. In the interior of thetubes 5 and 6, as shown in Fig. 1,'or at the exterior of the said tubes,as shown in Fig. 2, is disposed a cylinder 7 of carbon or likesubstance.

In the device shown in Fig. l the cylinder 7 may be solid or hollow, andin this latter case it may contain a solid refractory member 8 which issurrounded by a heat-insulating substance 9. This combination is closedby. a cover 10 of refractory material.

When a high frequency current flows.

through the winding 1, induction currents are produced at the peripheryof the carbon cyllnder 7 whereby it is brought to a high space 11 may bebrought to the temperature which is required in order to obtain thedesired crucible by the heating action. If

d the space 11' contains clay, bauxite, silica,

alumina, or the like, these substances must be heated to their softeningor melting point; if the said space contains mixtures of differentsubstances adapted for mutual reaction, the mixture must be raised tothe temperature at which this reaction will take place. This is the casein which the crucibles or like objects are to be made of sillimanite,and herein the space 11 is filled with a mixture of sand and alumina insuitable proportions; if the objects are to be made of carborundum, thesaid space contains a mixtureof sand and powdered carbon; if made ofzirconium carbide, the'space contains a mixture of zirconium andpowdered carbon, and so on. In other cases the mixture ma consist ofarefractor'y substance which orms the greater part of the crucible, towhich is added a certain percentage, usually, small, of another bodywhich is adapted to combine with the princi" al substance so as to bindits different partic es together. For example, the principal 'substancemay be zirconia, alumina, magnesia or the like, and. the secondarysubstance may consist of silica, carbon or the like. If the principalsubstance is alumina, and the secondary substance silica, I obtain afterheating the mixture to 1800 degrees a crucible consisting of grains ofalumina which are bound together by silicate of alumina or sillimanite.Numerous examples in which the said process is carried into effeet canthus be given. 7

Fig. 1 corresponds to the apparatus which is chiefly adapted for heatingthe interior of the crucible to be manufactured. Fig. 2 corresponds tothe case which is chiefly adapted for heating the exterior of thecrucible.

By the use of two carbon cylinders 7 comprising a thin cylinder at theexterior of the space 11, and a cylinder in the interior of the space11, I may effect the simultaneous heating of the interior and theexterior of said crucible.

In the apparatus shown in Fig. 3 it is desired tomanufacture a tube orlike hollow object from powdered substances which have no mutualcohesion; 12 is the inductance winding which consists of a copper tubeas.

in the example shown in Fig. 1. The tube 13 in which the object is to beformed is, in this example, capable of rotation, hence it is mounted ona disk 14 which is rotatable on a vertical or horizontal shaft by meansof the actuating device 15. In the tube 13, is disposed a refractor andheat-insulating envelope 16. In the interior of the tube 13 and coaxialtherewith is a cylindrical carbon (or graphite) block 17 which may belowered and is adapted to be held in a fixed position; said block may besuspended by a rod 18 of silica or the like, and it may be suitably ad.-'usted in height. In the space between said block and the tube 13 isplaced the substance or the mixture adapted to form the hollow object,such as a tube, which is to be obtained. Under the effect of centrifugalforc'e,*,the said substance is brought into contact with the internalwall ofthe envelope 16, and herein I employ a paper or pasteboard tube19 which will be carbonized, so that the object can be readily removed.The tube 13 is closed by a plug 20, and is guided in a collar 22. When ahigh. fre uency current is sent into the winding 12, induced currentswill be set up in the block 17 wherebyits surface portion will be highlheated. I may thus heat or melt the pow ered material placed in thespace 21 between the block 17 and the envelope 16 of the rotatable tube13. The action of centrifugal force upon the grains whereby they arepressed together will facilitate thelr agglom- V cent the block 17 andconcentrically with the latter, upon a thickness which can be variedwith the duration of the heating and the temperature of the block. Ifthe object thusproduced is not s'ufiiciently baked upon its outer face,this latter can be brought to the proper temperature by placing theobject for a certain time in another (carbon) crucible which is raisedto a high temperature by induced currents of high frequency, accordingto the arrangement shown in Fig. 2.

If it is desired to obtain an object which, is closed at the bottom,such as crucible, the

rotation of the disk 14 is slowed or even stopped at the end of theoperation, and the half-melted or entirely melted material will collectat the base in order to form the bottom part. 7

is desired to heat a hollow object which may have a great length, itbeing preliminarily mounted and agglomerated in the usual manner 23 isthe object to be heated, and it rests upon a disk 24 which may bestationary, or it may be rotated or given a vertical reciprocatingmotion. The inducing winding-25 is embedded in the internal wall of ablock 26 of an imperfect heat-conducting substance;

27 is the carbon (graphite) cylinder which isbrought to a very hightemperature by induc- In the example shown in Figs. 4 and 5 ittion bymeans of high frequency currents passing in the winding 25; the blocks2627 are suspended by means of the rods 28 to a cross bar 29, whichallows of modifying the relative ositions of the device thus formed andof th 23 can thus be gradually heated upon its e object to be heated.The object,

entire height by raising or lowering the object 23 or the devicesuspended from the bar 29.

Fig. 4 shows the apparatus employed for heating the interior oftheobject and Fig. 5

shows the apparatus for heating theexterior.

For the heating of the internal wall Fig.

4) the hollow'object 23 to be heated may be supported b an'outer moldconsisting of a dielectric substance, optionally combustible. Such anarrangement is used when the paste forming the said object has butlittle consistency.

I may also proceed as shown in Figs. 1 and 2. The ob ect 23 may besimultaneously heated by the use of a device comprising two cylinders 27whereof one is a thin cylinder placed at the exterior and the other isplaced in the interior.

Having nowdescribed my invention and in what manner the same is to beperformed, I declare that what I claim is;

1. In the art of making articles of a tubular shape, from comminuteddielectric material which is ca able of being sintered by heat, thesteps 0 including the comminuted material between concentric tubes ofpapery material, locating an inductance heating element in proximity toand parallel with such inclosed body of comminuted dielectric material,heating such heating element by induced currents to a suflicienttemperature to sinter the comminuted material into a coherent body andthereby carbonizing such sup-. porting tubes.

2. The process of baking objects of tubular form of a refractory anddielectric substance, by placin a piece of conducting heat resistingmateria capable of being heated to a high temperature by inducedcurrents, in the interior of the tubular object to be baked, in leavinga space between said piece and the object to be baked, thereafterheating the piece by means of induced electric current to a'temperaturesufficient to bake the object.

3. In the manufacture of objects of tubular form starting withcomminuted dielectric material capable of being sintered by 'heat, theprocess which consists in forming the comminuted material into a tubularshape, a tube of combustible material being interposed between the saidmaterial and the heating element, and in then heating the element bymeans of induced electric currents of high frequency to a temperaturesufiicient to sinter and agglomerate the comminuted material into asolid tubular body and in thus burning the tube of combustible material.

MARCEL FOURMENT.

